The present disclosure generally relates to radio frequency (RF) detection and ranging (RADAR) and, more particularly, to surveillance systems capable of discriminating living individuals from inanimate objects and detecting whether an individual may be carrying an object of interest such as a concealed weapon or an improvised explosive device (IED).
Portable, hand-held radars have been used for detection of hidden objects, e.g., objects such as weapons hidden behind a wall of a building. Such technology holds promise for use in situations where surveillance of an inhabitable area from behind a building wall may be desired, for example, for protection of an office space, with the detection system located inside the office, from individuals having access to hallways or areas nearby but outside the office. In some situations, e.g., police work, military combat scenarios, or fire and rescue situations, it may be desirable to be able to detect living individuals, and various objects that may be in their possession using a portable, hand-held radar system from outside a building, for example, occupied by the individuals.
An important case of detecting living individuals, and various objects that may be in their possession, is the detection of improvised explosive devices (IED) carried by a person. One of the most important and difficult aspects of the person-borne IED (PBIED) detection problem is reliable, verifiable interrogation of all individuals in an unstructured crowd at a large public event (e.g. a crowded market square). The Joint IED Defeat Organization (JIEDDO) is also interested in a more manageable problem of interrogation at controlled access points with, for example, individuals queued up in a one-at-a-time scenario for interrogation by portal or other fixed-site technologies (e.g. an election polling station). Such waiting lines represent targets of opportunity for bombers; therefore JIEDDO has been interested in solutions that address the crowd problem without requiring the cooperation or even knowledge of the individual being interrogated.